


goldenrod

by kinkymagnus



Series: tumblr prompts [2]
Category: Shadowhunters (TV)
Genre: Alpha Alec Lightwood, Alpha/Beta/Omega Dynamics, Bottom Magnus Bane, Cuddling, Enthusiastic Consent, Fluff, Heat Sex, Knotting, Light Dom/sub, Love, M/M, Mating Cycles/In Heat, Omega Magnus Bane, Plot What Plot/Porn Without Plot, Prompt Fill, Safe Sane and Consensual, Self-Lubrication, Smut, Top Alec Lightwood, Trust, Tumblr Prompts, but technically neither of them planned the heat thing and such, could be considered dubcon, like i don't see it that way as they're both eager and into it, mlm author
Language: English
Status: Completed
Published: 2018-08-12
Updated: 2018-08-12
Packaged: 2019-06-26 03:44:05
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,914
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15655080
Author URL: https://archiveofourown.org/users/kinkymagnus/pseuds/kinkymagnus
Summary: Most people present their second gender around the age of 21. Some, however, never present- these people are called Betas.Alec Lightwood had thought he was Beta, up until this moment.Turns out he's just a late bloomer.Or:Alec's having sex with his hot boyfriend when he suddenly presents and suddenly things get a lot more...heatedbetween them.Or:Turns out knotting someone can make them go into heat, even if you weren't previously aware said person was an omega. Who knew?





	goldenrod

**Author's Note:**

> this one is for anonymous, who wanted alpha/omega dynamics

 

“God, you’re so beautiful,” Alec says lowly, raggedly, his voice breathless and rough with _want._

Magnus moaned softly as Alec bit down gently on his neck, nipping and kissing at his skin.

Alec had always had a fondness for marking Magnus up, leaving hickeys all over Magnus’s body (but _especially_ his neck. and his thighs. and his collarbone. and his chest. fuck it, yeah, his whole body).

Maybe that should have been the first sign.

Magnus clutched at Alec’s back, fingertips pressed against the soft skin between his shoulder blades. “ _Fuck,_ ” he moaned.

Currently, Magnus was underneath Alec, back pressed to the sheets and strong arms wrapped around him. Alec was straddling him, one hand buried in Magnus’s hair, kissing up his neck. Alec licked a straight line up the side of his boyfriend’s throat, relishing the way Magnus shivered.

 “What do you want, baby?” Alec murmured, kissing behind his ear.

“I want _you,_ ” Magnus said, voice low and frustrated. “ _Please,_ Alexander…”

“Want me where?” Alec teased. “What do you want from me?”

“God, do you want me to beg?” Magnus moaned impatiently. “You know what I want, darling.”

“Do I?” Alec asked in a faux-innocent tone, kissing teasingly along his jawline. One arm had slid out from under him, hand cupping Magnus’s face and guiding him gently to the position Alec wanted, giving him further access to his neck.

Magnus tipped his head back obediently, groaning. Alec really wanted him to say it, didn’t he? Wanted him to _beg._

Magnus was more than happy to oblige—but Alec wasn’t the only one who could tease.

He gave his most wanton moan. “ _Please,_ Alexander,” he said in his most sultry, breathless tone.

Pausing for effect, Magnus let one trembling hand coming up to grasp the one cupping his face.

He guided Alec’s hand to his lips, taking his fingers between them, sucking gently.

Alec’s pupils were blown, hazel irises dark with desire. His hand was limp, allowing Magnus to wrap his soft lips around his fingertips.

“Fuck me,” Magnus moaned breathlessly, letting his fingers slip out for a moment. “I want your cock, Alexander, _please.”_

He made sure he sounded as seductive and needy as possible.

Those gorgeous lips, his _come hither_ eyes, and… _fuck,_ everything about him.

Alec pulled his hand aside, kissing Magnus again. Magnus hummed into the kiss, clearly pleased with himself.

Alec adjusted their position so that he was no longer sitting in Magnus’s lap, gently spreading Magnus’s thighs. Magnus languidly complied, laying back all the way and arching his back.

Alec grabbed a bottle of lube from the bedside table, coating his fingers then setting it aside, knowing he’d need it again soon.

He pressed his fingertips against Magnus’s hole. Magnus resisted the urge to whimper.

And Alec slid them inside.

Magnus choked on the whimper he’d been suppressing, eyes squeezing shut and lips falling open. Having two fingers knuckle-deep in his ass so suddenly felt _extremely_ good, if a little overwhelming.

Alec chuckled, and Magnus felt cool lips on his thighs. Alec kissed up his inner thigh, closer and closer to his cock, closer and closer to where two fingers were buried in Magnus’s ass, moving gently inside him.

Then the kisses got harder, open-mouthed and wet, and then he was scraping his teeth against Magnus’s sensitive skin, and then—he sucked mouth-shaped bruises up his thighs, switching back and forth, all while pumping his fingers in and out, getting faster and faster.

Magnus moaned loudly, hands coming down to grasp at Alec’s hair, fingers running through it like he was desperate for something to hang onto.

Alec slid another finger.

Magnus threw his head to the side, letting out a quiet, shuddering gasp.

Alec bent forward to lick gently at where Magnus’s hole stretched around his fingers. Magnus whimpered, ass clenching tighter.

Alec thrust his fingers in and out a little more, grazing his prostate and making him shudder with need.

But eventually, Alec pulled his fingers out, dragging them against his walls teasingly.

And then he pressed one last kiss to Magnus’s now loose hole before sitting up properly again.

Magnus sighed happily. “Mm… I love it when you do that,” he said. “But I do recall asking for your _cock,_ Alexander.”

“Good things come to those who wait,” Alec said, smirking at him. He crawled up Magnus’s body to kiss him properly. “Do you think you’re loose enough?”

“ _Yes,”_ Magnus said impatiently. “I’m ready. I just want your cock in me, Alexander, you’ve been teasing me all night.”

“Anything for you, beautiful,” Alec said, grabbing the bottle of lube again, generously slicking up his cock in preparation. After a moment, he tossed the bottle aside and positioned himself, pushing the blunt head of his cock between Magnus’s asscheeks.

And then he pushed forward, just slightly, dipping in just the head of his cock, stretching Magnus’s rim teasingly.

Magnus groaned. “ _Stop teasing.”_

Alec thrust forward, filling him completely in one go.

Magnus screamed, squeezing his eyes shut and clutching at the sheets one either side of him.

Alec was _thick,_ thick and hot and perfect and Magnus felt so _full_ and _fuck_ this was perfect—

He panted, taking a few moments to adjust, growing used to the hard cock splitting him open.

Alec was still, just watching the pleasure flickering over his boyfriend’s face.

“You ready for me start moving, baby?” Alec asked softly.

“Yes,” Magnus breathed. “Fuck. I need you, Alec.”

 _Alec,_ not Alexander. He really was wrecked, wasn’t he?

He pulled his hips back, shifting so that he could lean down and kiss at the shell of Magnus’s ear, and then thrust forwards, building up a pace. Magnus cried out with pleasure.

Alec fucked his boyfriend hard and good, thick cock pistoning in and out of him, slamming against his prostate over and over again. He ripped his mouth away from Magnus’s skin, adjusting to grab Magnus’s wrists and pin them over his head.

The noises Magnus was making got more urgent, gasping out Alec’s name and little moans of _yes_ and _please,_ struggling half-heartedly against his grip _._

He felt full and stimulated and needy and _god_ did this feel amazing, being held down and fucked by his boyfriend.

Alec thrust harder, rolling his hips roughly. Magnus was so _tight_ and _hot_ around him, slick and perfect, and Alec just couldn’t get enough of him.

Alec reached down, one hand still pinning Magnus’s above his head, and grabbed his hip, leveraging to change the angle of his thrusts. He punched a gasped moan from Magnus’s throat as he slid deeper, hitting his prostate head on. And then he grinded his hips, rubbing his cock right against his boyfriend’s sweet spot.

Magnus _whined,_ not even trying to fight Alec’s grip on his hands, just relaxing against the bed. He was completely content to lie back and let Alec take control.

Alec thrust into him, groaning. There was an odd sensation building in his cock—Magnus felt impossibly tighter, especially around the base of his dick, and he felt… strong. He needed _more._ Needed more of Magnus.

Magnus made a noise—startled and whimpering and gasping.

He could feel Alec’s cock swelling inside him, getting bigger in his ass. He felt heated and needy and _fuck fuck fuck this couldn’t be happening._

“A— _ah…_ Alec, you’re… _ahh…_ you’re—you’re knotting me…!” Magnus gasped.

Alec groaned, continuing to thrust into him. “I— _uh, fuck—_ do you want me to stop? Should I— _ahh—_ pull out—?”

“Fuck, no!” Magnus said. “Knot me, Alexander, _please.”_  

Hearing those words leave Magnus’s lips was somehow extremely hot.

Magnus felt hotter. The world was swimming around him. Only Alec felt real, everything else blurred.

He felt his ass get slicker, hotter, something warm and wet leaking from around Alec’s cock and dripping down his thighs.

“Alec, I— _nnng…_ I think… _fuck,_ I think your knot is triggering my heat,” he moaned. “I can’t—I can’t… _please…_ ”

“ _Fuck,_ you have a heat?” Alec panted.

“ _You’re_ the one with a knot,” Magnus moaned. “Please, just—I _need_ you…”

He was a little embarrassed about how needy and helpless he felt, how much he wanted to be filled and dominated. He’d only been in heat a few times in his long life, and never with an alpha. Alec knotting him must have been enough to trigger his heat and break through the medicine’s effects. He’d been on it so long it was no wonder that it had been enough… and it likely meant his heat was going to be very long and intense.

And it was all completely new to him, too. He’d never even been knotted before—and he’d certainly never imagined it would feel this good. Alec wasn’t even full-size yet and Magnus was already deliciously overwhelmed.

“I’m—I’m sorry, I didn’t know… I haven’t presented,” Alec said. His thrusts had, unfortunately, stilled, and he was panting against Magnus’s neck. “You know I wouldn’t have—done this without your consent. Should I…?”

Magnus shifted so he could sit up slightly, trying his best not to moan as Alec’s cock and half-mast knot moved inside him.

“I know that,” Magnus said quietly, “Of course I do. Just—don’t pull out. Please.”

"But you're... you're in heat, you're not..."

"I can think for myself," Magnus snapped. "I...  _please,_ Alexander.  _Alpha."_

It was very hard for him to focus on his words, attention diverted by the heat throbbing through him and Alec’s swollen cock in his ass, but he tried as hard as he could, refusing to let go.

"Magnus..."

“I—look, can we have this conversation later? Because I am… very, very hot right now, and I—I really need you, and I trust you and I love you and I  _know_ you’d never hurt me or take advantage of me and _please.”_

Magnus was rambling and he knew it, but he _really fucking needed_ Alec to fuck him, knot him, fill him up. His heat was getting worse and—Alec’s knot was beginning to go down as he focused on this instead of satisfying Magnus’s heat.

“Right,” Alec said, realization and determination in his voice. Magnus was asking him, _begging_ him even, and he wanted this. He was suffering and in heat and Alec had to finish what he started. “Oh god, I’m sorry. Of course. Come on, baby, lie back.”

He gently pushed Magnus back again, and Magnus relaxed against the bed.

Alec kissed him, swallowing the little noises Magnus made as Alec’s hips began moving again.

Alec was a little nervous—he’d never dealt with an omega in heat before, even platonically. Isabelle was an alpha and Jace was a beta and up until recently (recently being about five minutes ago), he’d thought he was a beta, too. And he’d never dated anyone else, either, so nothing there.

But Magnus did smell fucking delicious, and going by the very pleasured noises he was making, Alec wasn’t doing so bad.

And _god,_ he was so slick and hot, so fucking perfect around Alec’s cock.

“You’re so beautiful,” Alec whispered against his hot skin, thrusting into him harder and rougher, focusing on changing the angle and fucking deeper into him.

Magnus whimpered, throwing his head back. He could feel Alec’s knot swelling further in his ass, the hot and wet slide of his slick leaking from his stretched-out hole, the heat building all over his body, swirling and tingling and making his whole body a thousand times more sensitive.

The world was narrowed down to just Alec and him, wrapped up in their own little bubble of heat and lust and love.

“God, the noises you’re making, you’re so perfect,” Alec groaned, pausing between words to kiss messily up his neck. He sounded kind of out of it, lost in Magnus’s scent and perfect body. “Such a good omega. My wonderful, gorgeous omega.”

“Yours,” Magnus gasped out, head jerking in a desperate little nod. Then his eyes squeezed shut and he cried out. “Oh, _fuck,_ yes, _right there,_ please—”

Alec’s cock was sliding into him at the perfect angle, slamming into his prostate. His knot was still growing, very slow and steady but enough for Magnus to _feel_ it.

Magnus clenched around him, moaning and loving the sensation of that thick cock stretching him open, of the knot growing inside him, of feeling completely _full_.

Alec groaned at the way Magnus tightened around him, hauling him closer without slowing his thrusts.

Magnus was getting wetter, his scent getting much stronger as his heat rapidly grew more intense. His vision was a blur, eyes watering, voice cracking, and he was unable to stop the words pouring from his lips.

He was all gasping and mewling barely coherent things like “ _A—ahh… o-oh god, Alec, pl-please,  fuck me, harder, fuck me—”_ and “ _nhnnn…. so…_ so _big,_ please…. fuck, you feel so _good_ , alpha, please, _please…”_ and other rambling whines and praise for his fat, throbbing cock and huge knot, relishing the throbbing balls slapping against his ass with every thrust.

Magnus was embarrassed and almost _ashamed_ at the noises he was making. Both his mouth—the needy little desperate cries of Alec’s name that had devolved into whimpers and whines and begging for more… and his ass—the wet sounds of Alec’s cock sliding through his slick, the squelching noises (that had no right to sound so hot) of Alec’s knot popping in and out of his ass.

And then Alec’s hips were faltering, and the rough in-and-out slide of his cock was getting faster, his knot swelling faster, and then—

Magnus screamed, arching and involuntarily clenching down _hard_ as Alec’s knot finally grew to full-size and locked in his ass.

Alec was huge and throbbing, and Magnus’s eyes rolled back as Alec thrust in again.

He was still knotting Magnus but he seemed to be on autopilot. Even though he couldn’t pull his cock out, it didn’t stop him from grinding his hips down fiercely and teasing Magnus’s prostate.

Magnus was right on the brink of coming, pleasure burning through his body. He whimpered, feeling Alec’s lips hungrily mouthing at his skin, leaving hickeys and possessive marks up and down his neck. There were tears in his eyes, dribbling from his closed eyes even as his lips hung open.

He could barely hear what Alec was saying anymore, only the low, wrecked murmur of his voice, a comforting sound.

Then Alec groaned his name, loud and pleasured, pressing as close to Magnus as he could, curling in on himself as he pressed deep into Magnus and _came._

Magnus trembled, tense and tingling all over as he felt Alec’s cock twitching inside him, thick ropes of alpha cum pumping deep into him.

And finally, the tense lines of tension all snapped and all at once Magnus _let go._

He felt so _full_ and _satisfied_ and he’d never thought that he’d love this feeling so fucking much—the feeling of an alpha knotting him and filling his tight ass with seed.

But he _did._

He came on Alec’s cock, ass squeezing tight around his alpha’s knot, whole body shaking and practically vibrating as he screamed and whimpered with pleasure. His cock sprayed cum onto his chest, slick practically squirted out of him, leaking copiously from around Alec’s knot.

The heat raging through him was finally dwindling, dying down as his thoughts settled down and awareness came back to him.

Alec’s hips were still rocking minutely, riding the high and gently fucking Magnus through his orgasm.

Magnus moaned, feeling his body relax as the cock pumping seed into him finally began to sputter to a stop. Alec shifted on top of him, head swimming and dazed as he settled down on top of Magnus.

His cock was oversensitive and softening a little, but his knot stayed swollen and locked in his omega’s ass. It probably wouldn’t go down for a few hours, especially as this was their first time together like this.

He leaned down and kissed Magnus gently, hands gently running through his hair. Magnus gave a soft, pleased whine, wincing slightly at the soreness in his throat.

He was an utter mess—cum all over his abs, slick soaking his thighs, hair a complete mess sticking up in every direction, throat sore from all the moaning and screaming, ass plugged up and full of hot seed.

God, he was the most beautiful thing Alec had ever laid eyes on.

Alec nuzzled into his neck, kissing softly at his jawline.

Magnus sighed happily, letting Alec ravish him.

“I’ll get you all cleaned up,” Alec whispered, “I’ll take care of you, okay?”

“Wait ‘till your knot goes down, ‘kay?” Magnus said, words slurring slightly, sounding utterly content. “For now let’s just… cuddle.”

“Ohh, I can do that,” Alec mumbled, kissing the side of his head, right in front of his ear.

“Mmmm…. good,” Magnus said softly, letting his eyes fall shut. “I’m sleepy.”

It was only natural he’d be worn out after that stressful heat—and he seemed pretty fucking relaxed, too. No doubt he’d be fast asleep—supposedly, after a heat, omegas tended to have the best sleep of their lives.

 _Good,_ Alec thought, because if anyone deserved that it was Magnus.

He pulled Magnus closer, hugging him close, kissing his forehead. Magnus was already fast asleep in his arms, beautiful and relaxed and _so_ fucking perfect.

He’d stand watch, take care of his omega.

 _(His omega._ Shit, he’d have to think about the implications of _that_ later.)

 

It would be almost an hour before Alec’s knot went down.

Magnus woke to waves of warm and slick and cum leaking down his thighs, and to his alpha very gently and slowly sliding his cock from Magnus’s ass.

When his cock had completely slipped from Magnus, he pressed a kiss to Magnus’s forehead. Magnus stirred, moaning slightly.

He felt _empty,_ loose and slick, but he was too sleepy to move. His heat hadn’t restarted yet. He felt safe and relaxed in his alpha’s arms.

Alec gently lay him down, spread out on the bed and unmoving.

There was a long moment of silence, and Magnus wasn’t sure how long it stretched on because every moment felt warm and slow and dreamlike.

Then he felt a damp cloth on his stomach _(Alec must have gotten up and retrieved it)_ gently scrubbing away the mess they’d left on his skin.

Soon the cool, soothing touch moved down his stomach to his thighs, cleaning away the slick and cum from his skin.

Magnus felt like he was floating in and out of consciousness. His heat was still affecting him, even though it was currently dormant. Soon it would be strong enough to send him spiraling back down to where he’d been earlier—slick and sensitive and squealing as Alec pounded into his ass.

A light shiver ran down his spine. He couldn’t wait.

 

They were lying on their backs next to each other, panting and sated.

Magnus was more relaxed than he’d ever felt, his thighs still slightly damp with the cool water Alec had cleaned them with. Every muscle was warm and lax, his breathing deep and even. But he felt more awake and aware than he had, no longer lost in a dreamy haze.

Alec was lying next to him, arm stretched out so that his hand rested gently on Magnus’s. The sheets were pulled up to their waists. The room was quiet.

Magnus broke the comfortable silence.

“I’m sorry I didn’t tell you about… _this_ sooner. I just didn’t think it was… relevant. I’ve been taking suppressants for centuries, and I’ve never even been with an alpha. I’ve never even told anyone but my two closest friends that I’m not a beta. And since I thought you were a beta…”

His voice trailed off.

“Would you have ever told me?” Alec asked. He didn’t sound mad, only curious.

“I think so,” Magnus sighed. “I don’t know. It’s a big secret, one I’ve kept all my life… but I don’t think I’ve ever trusted anyone the way I trust you. And I’ve certainly never trusted an alpha the way I trust you.”

“W-would you… have been with me, trusted me, if you’d known from the beginning?” Alec asked hesitantly.

“I don’t know,” Magnus admitted. “I mean, I knew you were a shadowhunter, but I grew to trust you anyway. I think… I think it wouldn’t have mattered.”

“I don’t blame you for not telling me, you know,” Alec said, taking his hand properly and squeezing it gently.

Magnus bit back a smile. “Thank you,” he said softly.

There was a moment of silence, but Alec couldn’t bear it for too long. He had too many questions.

“So how did I activate your heat, anyway?” Alec asked, turning on his side to face Magnus more fully.

Magnus turned over to face him, too, fingers playing with Alec’s nervously. The sheets were pooled enticingly around his hips. “Well, like I said. I’ve been on suppressants for centuries. And… I’ve never actually been with an alpha before. I suppose not allowing myself to go into heat for so long took its toll. And the medicine was probably weakened over time.”

“And why didn’t you let yourself go into heat?” Alec asked curiously.

Magnus’s gaze flitted away. “I…” he began hesitantly. “I never trusted anyone enough to help me through it. I didn’t want to put myself in such a vulnerable position, let alone without an alpha I trusted.”

“Oh, god,” Alec said, sounding horrified, withdrawing his hand as if he was afraid to touch him. “And I just… forced you. You slept with me not knowing I was an alpha, I—I knotted you without permission, I drove you into heat with no warning—”

“Alec,” Magnus said, trying to speak over him. “ _Alec,_ stop.”

Alec’s mouth snapped shut, eyes wide and worried.

Magnus scooched closer, taking his hand again. “Alec, it’s okay. No, hear me out, okay, it’s _okay._ I _trust_ you. And yes, you knotted me but… you never, not _once,_ forced me. And yes, I slept with you not knowing you were an alpha, but _you_ didn’t know either! There’s no way you could have. Hell, we’ve slept together before and this has never happened. And besides, I’m not blameless here, either! I never told you I was an omega, did I?”

“That’s different,” Alec said, “You being an omega doesn’t give you any sort of power over me.” But he didn’t pull back.

“The only power you have over me is the power I give you,” Magnus said quietly. “Which is a lot, but all voluntary and consensual because I _trust you.”_

“But when you’re in heat…” Alec trailed off.

“It’s _okay,”_ Magnus said again, firm and soft. “Look, my heat cycle isn’t over. Considering how long I’ve been suppressing this, it’ll probably be all week at the _least_.”

“Do you want me to—to leave? Get help? I—”

“Jesus, _no._ Alec, I want _you._ This is me, not heat-addled, telling you that I trust you and I _want_ you to do this.”

“…are you sure?” Alec asked quietly.

“Completely,” Magnus said, voice soft and sincere. He leant up to kiss Alec’s lips, gentle and chaste. After a moment, Alec kissed back, hand coming up to cup his face.

As they pulled away, Magnus said softly, “I love you, Alexander.”

“I love you, too,” Alec murmured, kissing him again.

 

 

**Author's Note:**

> if you want to submit a prompt from [this](https://kinkymagnus.tumblr.com/post/175070176809/nsfw-malec-prompt-list) list just go to [my tumblr!](kinkymagnus.tumblr.com/ask)  
> some of them are pretty kinky i mean y'all can submit any numbers on that list so  
> try to keep it to like, one prompt per person tho, k? 
> 
>  
> 
> might make this into a series. maybe some more kinky drabbles or something. or at least, use any other a/b/o prompts to play with this a little. honestly, i've always liked alpha/omega dynamics, i wouldn't mind playing with them a bit.
> 
> and okay if you're wondering about the title: a) goldenrod is a type of late blooming flower. so. ha. b) goldenrod sounds like a sex joke or a bad porno. possibly a porn parody of a bond movie. c) seriously like maybe this fic is about magnus wanting alecs 's "goldenrod" if you know what i mean wink wink  
> ....okay so i just couldn't think of a good title sue me


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